1. Field of the Invention
This invention relates to adjustable rail anchorage arrangements which are subject to very large lateral loads applied to the rails, particularly in crane rails by cranes as they travel along the rails, being cranes used for material handling in industrial facilities. Such cranes travel along rails which are supported generally on steel structures, the rails being maintained in the required position by rail anchorages that have to ensure that the rails remain located when very substantial lateral loads are generated, for example, when the crane is in motion. It is therefore important that the rails properly guide the cranes by being correctly aligned. Poorly aligned rails result in crane wheel wear and wear to the sides of the rail head and cause the crane to skew and bind against the rail. As a consequence even larger lateral forces can be generated on to the rail as the crane skews and binds. By providing an anchorage that is laterally adjustable the lateral alignment of the rail can be more easily established and maintained. However, when the rail anchorages offer adjustability other problems can occur. They can slip due to contamination by oil and grease which can drip from the crane axle and bearings as the crane travels along the rail. The oil and grease can lubricate the sliding surfaces of the adjustable anchorage. Also, adjustable rail anchorages are generally installed by a threaded bolt or threaded stud which requires careful attention that adequate torque is applied to the bolt or nut in order to prevent slipping of the anchorage.
2. Description of the Prior Art
Cam devices have been used in rail anchorage arrangements as a means of adjustment. Attempts have been made to prevent untoward cam rotation by use of incremental locking positions, which have the result that only incremental adjustments are possible. The bolt or other fastening device provided has been placed centrally within a hole in the cam. In the prior art the application of the lateral load from the rail to the clip does not increase the frictional resistance of the cam against rotation within the rail clip.